This invention relates to a probe stabilized arc discharge lamp usually operated in a pulsed mode.
Arc discharge lamps are used for spectroscopy, as sources of light with a response over a broad spectrum, and for many other uses. Most arc discharge lamps have several components in common: an arc gap defined by two opposing electrodes, one of which is a cathode, another being an anode, disposed in a gas (e.g., Xenon) filled chamber. A reflector is typically disposed about the arc gap and light emitted at the arc gap is directed by the reflector out a window.
There are two basic types of arc discharge lamps: those designed to operate in a continuous mode and those designed to be operated in a pulsed mode. Typically, arc discharge lamps designed to be operated in a continuous mode cannot generally be operated in a pulsed mode because of, inter alia, the differences in the internal pressures generated, the lack of a trigger probe in continuously operated lamps, the increased cathode and anode sputtering which occurs in the pulse mode and the criticality of cathode and anode alignment in pulsed mode lamps.
Therefore, continuous mode lamps, if operated in a pulsed mode, would suffer from a short useful life and a less than desirable output. There are also two basic continuous mode lamp designs: those with horizontally disposed cathodes and anodes, and those with vertically disposed cathodes and anodes. By horizontally disposed electrodes, we mean electrodes disposed across the light path from the arc gap to the reflector and out through the window. By vertically disposed electrodes, we mean electrodes extending in the direction of the light path. The vertically disposed cathode and anode design advantageously has an improved lambertian distribution because the arc gap can be set at the focal point of the reflector and there is a minimum of structure disposed in the light path between the arc gap and the window.
Today, however, all successful pulsed mode arc discharge lamp designs have included only horizontally disposed electrodes. But, because of the benefits of vertically disposed electrodes in continuous mode arc discharge lamps, as discussed above, those skilled in the art have long desired a pulsed mode arc discharge lamp with vertically disposed electrodes. Due to the required physical differences between pulsed mode and continuous mode arc discharge lamps, however, the design of a continuous mode arc discharge lamp with vertically disposed electrodes has not translated into a successful pulsed mode arc discharge lamp design with vertically disposed electrodes.
Disclosed herein is a probe stabilized short arc discharge lamp designed to be operated in a pulse mode and advantageously having vertically disposed electrodes made possible, inter alia, by unique cathode and anode configurations, a uniquely designed trigger probe electrode, a preionization device called a sparker, monolithically constructed ceramic housing with a reflector integrally disposed thereon, a novel cathode jig for co-axially aligning and correctly distancing the cathode with respect to the anode, and a novel trigger probe jig for orienting the probe tip with respect to the arc gap. And, preferably, all of the electrode connections extend through the base of the lamp.
It is therefore an object of this invention to provide a high output, long life arc discharge lamp designed to be operated in a pulsed mode.
It is a further object of this invention to provide such an arc discharge lamp with vertically disposed electrodes.
It is a further object of this invention to provide such an arc discharge lamp with integrated optical components.
It is a further object of this invention to provide such an arc discharge lamp which can be operated at a high pressure.
It is a further object of this invention to provide a more efficient arc discharge lamp.
It is a further object of this invention to provide such an arc discharge lamp with improved lambertian distribution.
It is a further object of this invention to provide an arc discharge lamp with increased stability.
It is a further object of this invention to provide an arc discharge lamp which requires less power to operate for a given output.
It is a further object of this invention to provide such an arc discharge lamp which lasts longer.
It is a further object of this invention to provide such an arc discharge lamp which does not exhibit excessive sputtering.
It is a further object of this invention to provide such an arc discharge lamp which does not suffer from breakdown potentials.
It is a further object of this invention to provide an arc discharge lamp which is single ended: that is, all the electrical connections extend from the base portion of the lamp.
It is a further object of this invention to provide such an arc discharge lamp which is relatively easy and inexpensive to manufacture.
It is a further object of this invention to provide such an arc discharge lamp which can be repeatedly assembled in an exacting configuration.
It is a further object of this invention to provide a cathode jig for co-axially aligning and correctly distancing the cathode with respect to the anode.
It is a further object of this invention to provide a trigger probe jig which correctly orients the trigger probe tip with respect to the arc gap.
In this invention, the advantages of vertically disposed electrodes are realized in a pulsed mode arc discharge lamp by a uniquely configured anode and cathode, the presence of a trigger probe, a preionization device call a sparker, a monolithically constructed base and side wall lamp housing portion typically made of ceramic material, an integral reflector constructed directly on the ceramic housing, the use of a novel cathode jig which assists manufacturing personnel in co-axially aligning and correctly distancing the cathode with respect to the anode, and a novel trigger probe jig which assists manufacturing personnel in correctly orienting the probe tip with respect to the arc gap.
This invention features a probe stabilized arc discharge lamp. Typically, the lamp includes a monolithic base portion and side wall portion defining a concave surface, a window spaced from the base portion and sealed with respect to the side wall portion defining a chamber, a gas in the chamber, and a reflector disposed on or integral with the concave surface. A first electrode is usually centrally disposed in the base portion and has a distal end which extends outwardly from the base portion. In the preferred embodiment, the first electrode includes an anode support and an anode vertically supported by the anode support. Also in the preferred embodiment, there is a second electrode also having a distal end which extends outwardly from the base portion. The second electrode preferably includes a cathode support extending vertically upward through the side wall portion, a cathode support arm extending horizontally inward from the cathode support, and a cathode extending vertically downward from the cathode support arm to a location spaced from the anode to define an arc gap at the focal point of the reflector. Finally, a third electrode is preferably included which also has a distal end extending outwardly from the base portion. The third electrode extends vertically upward through the side wall portion and has a reduced circumference region or probe support pin proximate the side wall portion. The third electrode further includes a trigger probe extending from the reduced circumference region to or proximate to the arc gap for triggering an arc in the arc gap between the anode and the electrode.
In one example, the base portion and the side wall portion are made of a ceramic material, the anode support includes a distal seat for receiving the anode, the anode support is made of Kovar, the anode has a flat distal surface with no chamfers, the cathode support is made of Kovar, the cathode support arm is made of molybdenum, the cathode is made of a material including tungsten and the cathode has a pointed and tapered distal (e.g., 60xc2x0 tapered) end.
The cathode support may have a recess on a distal end thereof for receiving one end of the cathode support arm and the cathode then has a recess on a proximal end thereof for receiving the other end of the cathode support arm.
In one preferred embodiment, third electrode includes a support extending upward through the side wall portion, a probe pin extending upward from the support, the probe pin having a reduced circumference, and a probe which extends from the probe pin. The support typically includes seat therein for receiving the probe pin.
The window may be made of sapphire, may be flat or convex in shape, and may include a transparent member surrounded by a collar which is secured to the side wall portion. Further included may be a shield member extending about the collar and a portion of the side wall. In one embodiment, the side wall portion includes an integral support for the window.
The reflector may be parabolic or elliptical in shape and preferably terminates on the side wall portion at a location spaced from the cathode support and also at a location spaced from the reduced circumference region of the third electrode. Typically, the trigger probe has a pointed distal tip offset from the arc gap.
The probe stabilized arc discharge lamp of this invention may comprise a base portion; a window spaced from the base portion; a side wall interconnecting the base portion with the window such that the side wall, the base portion, and the window define a gas containing chamber; a first electrode disposed vertically in the chamber and extending outwardly through the base portion; a second electrode also disposed vertically in the chamber and extending outwardly through the base portion, the second electrode spaced from the first electrode defining an arc gap between distal ends of the first and second electrodes; a trigger probe extending to or proximate to the arc gap for triggering an arc in the arc gap; and a reflector disposed about the arc gap for directing radiation generated by the arc out the window.
Preferably, the base portion and the side wall are monolithic in construction and define a concave surface surrounding the arc gap. The base portion and the side wall are typically made of ceramic material and the reflector is preferably an integral part of the concave surface.
The second electrode preferably includes a cathode support extending up through the side wall, a cathode support arm extending horizontally from the cathode support inwardly over the arc gap, and a cathode extending vertically downward from the cathode support arm. The cathode support may have a recess on a distal end thereof for receiving one end of the cathode support arm and the cathode then has a recess on a proximal end thereof for receiving the other end of the cathode support arm.
The trigger probe is preferably disposed on one end on a probe support electrode which extends outwardly thought the base portion. The probe support electrode includes a seat on a distal end thereof, the lamp further including a reduced circumference trigger probe support pin supported on one end by the seat in the probe support electrode. The trigger probe extends inwardly and downward from the trigger probe support pin.
The lamp preferably also includes a sparker assembly including a lead disposed in the chamber, an insulative support for the lead attached to the cathode support arm, and an electrical conductor extending to and within the gas fill tube.
A probe stabilized arc discharge lamp according to this invention includes a base portion; a window spaced from the base portion; a side wall interconnecting the base portion with the window, the side wall, the base portion, and the window defining a chamber; a gas in the chamber; a first electrode disposed vertically in the chamber and extending outwardly through the base portion; a second electrode also disposed vertically in the chamber and extending outwardly through the base portion, the second electrode spaced from the first electrode defining an arc gap between the distal ends of the first and second electrodes; a trigger probe extending to or proximate to the arc gap for triggering an arc in the arc gap; and a reflector disposed about the arc gap for directing radiation generated by the arc out the window.
This invention also features a cathode jig for a probe stabilized arc discharge lamp, the cathode jig comprising a multiple piece body having a first section with an internal channel for receiving an anode therein and a second section with a concave cavity on the distal end thereof for receiving the distal end of a cathode; the first section having a circumference sized to coaxially align the cathode with the anode when the first section is disposed over the anode; and the second section having a length sized to correctly distance the distal end of the cathode from the distal end of the anode. In one example, the multiple piece body is divided into two pieces.
This invention also features a trigger probe jig for a probe stabilized arc discharged lamp, the trigger probe jig comprising a multiple piece body having an internal channel for receiving an anode therein and a distal end with a rest defined thereon for receiving and supporting the distal end of the trigger probe, the body having a circumference and a length sized to correctly orient the trigger probe tip with respect to the arc gap between the cathode and the anode.